Protective wall, dyke and method of producing a dyke

ABSTRACT

The protective wall ( 5 ) has a flat, tabular or cubic configuration which has a section of a water-impermeable building material. The building material of the protective wall is a compound of compacted, mineral aggregates and an organic adhesive. Mineral aggregates such as sand or gravel are building materials which occur in plentiful amounts in nature and can be acquired simply and inexpensively in large quantities on-site. Mixed with an organic adhesive, the building material has a viscous consistency and can be produced and processed easily. By means of appropriate shaping, the protective wall can be configured in a variety of dimensions, frequently curved. The protective wall is suitable for sealing dykes to protect them against erosion in coastal or liquid-side high-water protection.

The invention relates to a protective wall according to the preamble of patent claim 1. It also relates to a dyke according to the preambles of patent claims 12 and 15 and to a method of producing a dyke according to the preamble of patent claim 24.

Two centuries of floods in only five years have again made it directly clear to people in Germany the power and the hazard potential of rising floods and other bodies of water. Attempts are made to improve the level of protection by the construction of technical flood prevention measures such as dykes, barrages, retention basins and other protective installations (protective walls). In this case, special importance is attached to the construction of dykes at rivers and coasts.

The trapezoidal cross section of a dyke is typical of its type of construction. The dyke body usually consists of compacted earth or construction materials with a firm, effectively rooted grass cover or of a mixture of various earth and construction materials. For reasons of stability, the slopes should be 1:3 or flatter, which also brings about advantages during maintenance and with regard to requisite measures against wild animals. The slopes at river courses are as a rule between 1:2 and 1:3, whereas the slopes at coasts may also be designed to be flatter, at least on the sea side.

The crown height of the dykes is based essentially on the selection of the design flood as an event with a certain probability of occurrence (recurrence within a certain period of time) relative to a certain water level. It is calculated from the high-water level and the “freeboard” (additional height for raising of the water level by the wind, wave run-up on the slope, possibly the effect of an ice jam, and an increased factor of safety). In the case of new construction, there is also an additional factor for the settling of the subsoil and the dyke body.

Seepage through the dyke, underflow of the dyke and the safe dissipation of the seepage water are also factors determining the cross section. High water levels continuing for a long time and rapidly falling water levels impair the stability of the dyke. The risk of the dyke fracturing increases with the intensity and duration of the inundation.

If underflow of a dyke occurs, movements of material and further erosion occur, which make the dyke increasingly unstable. The hydraulic loading of the dyke body is also enormous in particular during a flood; if it becomes too great, the dyke body becomes soaked throughout and the water flows out of the dyke on the side facing away from the river or sea.

As an ideal dyke construction with regard to stability in the case of a flood continuing for a long time, the three-zone dyke cross section has proved successful: a permeable earth supporting body having a water-side wedge of less permeable earth material, said body, if required for lengthening the flow path, being integrated with a sealing wall (curtain wall, thin diaphragm wall, sheet pile wall) in the subsoil under the dyke or in a deeper-lying dense stratum. Such a dyke has been disclosed, for example, by WO 00/34587. Provided here is a waterproof barrier which extends in the dyke longitudinal direction and vertically up to below the dyke crown. The barrier is positioned approximately centrally between the two slopes. The barrier is of multi-piece construction and has a waterproof membrane in the center made of a synthetic material. The membrane is fixed laterally in a foundation in a membrane section folded like a bellows.

In another embodiment, a dyke revetment for protecting the slope from penetrating water is provided. Serving for this purpose is a multi-layered, waterproof membrane which is anchored in the slope.

Proceeding therefrom, the object of the invention is to specify a protective wall of the generic type which effectively prevents or markedly reduces the erosion of a coast or a bank. The protective wall is to be capable of being produced at a low cost of construction. The object of the invention is also to specify dykes of the generic type which have improved protection against erosion and can be produced at a low cost of construction. In addition, a method of producing a dyke is to be specified.

According to the invention, the object with respect to the protective wall is achieved by the features of claim 1.

The protective wall has a planar, plate-shaped or cubic design which has a section made of a waterproof construction material. The construction material of the protective wall is a compound of compacted, mineral aggregates and an organic adhesive. Mineral aggregates such as, for example, sand and gravel are construction materials available in abundance in nature and can be procured on site in large quantities in a simple and inexpensive manner. Mixed with an organic adhesive, the construction material can easily be produced and processed in a viscous consistency. The protective wall can be extended in a variety of ways, often in a curved manner, by appropriate shaping.

In this connection, the good flowability is of great importance for the processing. In the uncured state, the construction material, in most combinations, has higher flowability (consistency class) than freshly mixed concrete.

For the processing of the construction material in the tidal zone or in the case of wet gravel, it is appropriate to use an adhesive that can be cured under the effect of water. Other suitable adhesives are a two-component epoxy resin adhesive, a single-component polyurethane adhesive or a two-component polyurethane adhesive.

The grain size of the aggregates is preferably between 0.1 and 0.3 mm. Good water tightness is still provided for within this range without the screening of the construction materials having to become too restricted. Ideally, the permeability coefficient k_(f) of the construction material is at most 5×10⁻¹⁰ m/s.

If larger grain sizes are used, the water permeability increases. The protective wall is then suitable, when arranged in the slope region of a dyke, as water bottom and bank protection and helps to act against erosion in the coastal and bank region, in which waves or the wave run-up is/are decelerated and absorbed. In this case, favorable grain sizes of the aggregates are preferably between 2 and 150 mm.

The density of the protective wall is also favorable, which density is higher than that of water and if need be can be increased and varied by the addition of steel. The protective wall is therefore effectively prevented from being washed away especially in the region of the breakers.

A further advantage lies in the environmental compatibility of the construction material. When two-component epoxy resin adhesive is used as organic adhesive, for example, the construction material has no toxic effect at all on mold fungi and is difficult to break down microbially. Nonetheless, substances that can be eluted from the protective wall can be readily broken down, as material tests have shown. As washing tests prove, there is no chemical interaction between water and the constituents of the construction material. The protective wall can therefore even be used in dams and enclosures for drinking water reservoirs.

Finally, after its useful phase, the ground covering according to the invention can be disposed of in a washing plant for earth or gravel without adverse environmental effects. Alternatively, after comminution, reuse as granulated material is also possible.

In another embodiment, the wall thickness d_(w) of the protective wall is smaller than the extent in height h_(w) and length l_(w). Thus, for example, mat-shaped protective walls can be produced on site with adhesively bonded gravel and can then be sunk in the water on a floating pontoon in order to be used as water bottom protection against erosion (harbors, sheet pile walls, etc.). Protective walls in a length of 40 m max, a width of up to 25 m and a thickness of up to 50 cm can be processed in a prefabricated manner on the construction site.

With regard to the dyke, the object is achieved according to the invention by the features of claim 12.

The dyke has a dyke body having an essentially trapezoidal cross section. A dimensionally stable protective wall is provided between the inner slope and outer slope and extends in the dyke longitudinal and vertical directions, the protective wall being designed according to one of the exemplary embodiments described above.

In this case, the protective wall acts as a seal. The seal reduces the seepage water quantities and contributes to the stability of the dyke. Surface seals on the water side, as are explained later with respect to the alternative achievement of the object of the invention according to the features of claim 15, and core seals (inner seals) are possible. The protective wall preferably runs in the dyke body vertically from the dyke crown through the dyke cross section and is integrated in the ideal case in a dense soil stratum underpinning the dyke. The protective wall avoids underflow of the dyke, which underflow would result in material movements and further erosion, which make the dyke increasingly unstable.

A barrage sealed in such a way can be designed with steeper slope angles, as a result of which the dyke cross section can be reduced, which is of additional advantage in restricted spatial conditions. Asymmetrical positioning of the protective wall with an offset relative to one of the two slopes is possible as a further variant, the positioning on the water side further reducing erosion in the slope on the water side.

Protective walls can also be installed subsequently in already existing dyke structures and constitute a simple and efficient method of strengthening and repairing dykes.

A further solution according to the invention that achieves the object with respect to the dyke is provided for by the features of claim 15.

According to the invention, the dyke has a made-up dyke body comprising a slope on the water side and land side, a dimensionally stable protective wall being situated in front of the water-side slope. The protective wall is designed according to one of the exemplary embodiments explained above. Favorable angles of inclination α of the protective wall relative to the water surface lie between 15 and 90 degrees, it being possible for the angle of inclination α to differ from the slope angle β if, for example, the protective wall is separately embodied such as to be removed from the slope. For reliable anchoring of the protective wall, said protective wall can be fastened by an additional base in the region of the dyke toe, the slope and/or in the foundation.

The dyke according to the invention has the advantage that effective slope protection is provided for when positioning close to the bank or to the coast and in the case of dykes with a lower-lying narrow foreshore. A closed, dense and strongly rooted grass cover offers as a rule, for dykes, sufficient and efficient slope protection against flow and wave attack. There is also effective protection against flotsam (e.g. including tree trunks, possibly drifting ice floes and ice jam in winter). This also applies in the case of frequently recurring high water levels continuing for a long time.

Enhanced sealing against underflow and seepage can be effected by virtue of the fact that the protective wall extends from the dyke body right into the foundation.

The invention permits the construction of steep slopes (steeper than 1:3), since it protects the dyke body against damage when embodied as planar protection. In the case of a rapidly falling water level, a heavy and water-permeable protective wall as (open) revetment is required for reasons of stability. An advantageous property of the invention, according to which the water permeability of the protective wall can be determined according to the selection of the grain size, becomes noticeable here. If the protective wall is to be designed to be water-permeable as for the above application, grain sizes of roughly above 2 mm should be used for the mineral aggregates. The grain size for a waterproof protective wall is accordingly below this.

A dyke having a protective wall which extends into the dyke body is constructed by the following method steps:

-   -   incorporating a trench which extends from the dyke crown or the         slope into the depth of the dyke body and in the longitudinal         direction of the dyke,     -   filling the trench with a protective wall made of a construction         material consisting of mineral aggregates and an organic         adhesive,     -   compacting the construction material, and     -   curing the construction material.

In a type of construction in which the protective wall is put onto the slope, the gravel is in each case applied in layers up to a height of 300 mm and is then adhesively bonded with an organic adhesive.

Advantageous embodiments of the invention are explained below with reference to the attached drawing, in which:

FIG. 1 shows a dyke, designed according to the prior art, without a protective wall,

FIG. 2 shows a schematic cross section of a dyke having a protective wall extending into the dyke body,

FIG. 3 shows a schematic cross section of a dyke having a protective wall put onto the slope, and

FIG. 4 shows a cross section of a dyke having a protective wall put on a base.

FIG. 1 shows the typically trapezoidal cross section of a dyke. The dyke body 1 is constructed above the foundation 2. In the region of the foundation 2, over the entire width of the dyke, the “dyke bed”, the dyke body 1 runs out into tongue-shaped banquettes 3 on the water and land side.

The dyke body 1 terminates at the top with the dyke crown 4. It is usually inclined or arched for draining toward the water. If not negotiable, it is protected against erosion (earth removal) by sods. If the dyke crown 4 is used for inspection with lightweight vehicles or for bicycle traffic, a paving is required. Banquettes 3 placed on the land side increase the stability and carry as a rule the dyke defense path which serves for the maintenance of the dyke and, in the event of extreme flooding, for the defense of the dyke. With regard to route directing, dimensions and paving, the dyke defense paths must therefore permit speedy, risk-free flow of traffic in an extreme situation and must be able to absorb the loading by heavy vehicles and equipment.

Shown in FIG. 2 on the basis of the fundamental type of construction of a dyke is a first embodiment of the invention, in which the trapezoidal dyke body 1 has a vertical protective wall 5 for sealing it against erosion. The essentially flat, plate-shaped protective wall 5 extends in the longitudinal direction of the dyke and in its height from the foundation 2 right up to the dyke crown 4. Roughly one fifth of the height of the protective wall 5 extends into the foundation 2. With its crown-side end, the protective wall 5 terminates flush with the dyke crown 4 and could serve as part of a dyke path (not shown in any more detail). In further sections (not shown) of the dyke, the protective wall 5 also extends beyond the dyke crown 4. In its longitudinal direction, the protective wall 5 is composed of a plurality of wall elements adjoining one another. As can be seen, the wall thickness d_(w) of the protective wall 5 is markedly smaller than the extent in height h_(w) and length l_(w).

The construction material of the protective wall 5 is a compound of sand and an organic adhesive. Mineral aggregates such as, for example, sand. The grain size is between 0.1 and 0.3 mm; therefore the protective wall is virtually watertight and thus prevents soaking or flushing of the dyke body.

A second embodiment of a dyke can be seen in FIG. 3. There, the protective wall 5 is inclined at an angle of inclination α to the plane of the foundation 2 and is put onto the water-side slope 6. In this embodiment, the angle of inclination α is equal to the slope angle β. The height h_(w) of the protective wall 5 projects just above the design high-water level. On the base side, the protective wall extends right under the low-water level in order to avoid erosion even at low water and make possible reliable anchoring.

An embodiment having improved stability of the slope-side protective wall 5 in comparison with the second embodiment is shown with the third exemplary embodiment in FIG. 4. Here, a base 7 anchored in the water-side slope 6 serves for fixing the protective wall 5 against drifting or sagging in the event of underscouring.

In the second and third embodiments of the protective wall 5, watertight or water-permeable compositions of the mineral aggregates are possible.

Of great advantage in the production of the protective walls 5 is the fact that sand as a mineral aggregate in applications near the coast is of course available in practically unlimited quantities.

List of Designations

1 Dyke body

2 Foundation

3 Banquette

4 Dyke crown

5 Protective wall

6 Slope

7 Base

α Angle of inclination

β Slope angle

d_(w) Wall thickness

h_(w) Height

l_(w) Length 

1. A protective wall, in particular for dykes of river banks and coasts, comprising a planar, plate-shaped or cubic design, the protective wall having at least one section which is extended in the longitudinal and vertical directions and is made of a waterproof construction material, the construction material of the protective wall being a compound of compacted, mineral aggregates and an organic adhesive.
 2. The protective wall as claimed in claim 1, wherein the construction material has higher flowability than freshly mixed concrete in the uncured state.
 3. The protective wall as claimed in claim 1 wherein the grain size of the aggregates is 0.1 to 0.3 mm.
 4. The protective wall as claimed in claim 1 wherein the grain size of the aggregates is 2 to 150 mm.
 5. The protective wall as claimed in claim 1 wherein the mineral aggregates comprise at least one of sand and gravel.
 6. The protective wall as claimed in claim 1 wherein the adhesive is an adhesive that can be cured under the effect of water.
 7. The protective wall as claimed in claim 1 wherein the adhesive is one of a two-component epoxy resin adhesive, a single-component polyurethane adhesive, and a two-component polyurethane adhesive.
 8. The protective wall as claimed in claim 1 wherein the permeability coefficient k_(f) of the construction material is at most 5×10⁻¹⁰ m/s.
 9. The protective wall as claimed in claim 1 wherein the density of the protective wall is greater than that of water.
 10. The protective wall as claimed in claim 1 wherein the protective wall has an addition of steel.
 11. The protective wall as claimed in claim 1 wherein the wall thickness d_(w) of the protective wall is smaller than the wall's extent in height h_(w) and length l_(w).
 12. A dyke, in particular for river and sea dykes, comprising a dyke body which essentially has a trapezoidal cross section, the dyke having a dimensionally stable protective wall formed between an inner slope and an outer slope and extending in the dyke longitudinal and vertical directions; wherein the dyke has a protective wall designed according to claim
 1. 13. The dyke as claimed in claim 12, wherein the protective wall extends right under the dyke body into a foundation.
 14. The dyke as claimed in claim 12 wherein the protective wall extends right into one of a dyke crown and ends at one of the inner slope and the outer slope.
 15. A dyke, in particular for river and sea dykes, comprising a made-up dyke body and a slope on the water side and land side; and a dimensionally stable protective wall being situated in front of the water-side slope; wherein the dyke has a protective wall designed according to claim
 1. 16. The dyke as claimed in claim 15, wherein the protective wall rests on the slope.
 17. The dyke as claimed in claim 15 wherein the protective wall has an angle of inclination α of 15 to 90 degrees relative to the water surface.
 18. The dyke as claimed in claim 17, wherein the angle of inclination α is equal to a slope angle β.
 19. The dyke as claimed in claim 12 wherein the dyke has a base which is anchored in at least one of the slope a foundation and carries the protective wall.
 20. The dyke as claimed in claim 12 wherein the protective wall extends from the dyke body into a foundation.
 21. The dyke as claimed in claim 12 wherein the dyke has a plurality of wall elements which adjoin one another in the dyke longitudinal direction.
 22. The dyke as claimed in claim 12 wherein the dyke has a plurality of wall elements staggered in a depth direction of the dyke.
 23. The dyke as claimed in claim 22, wherein the wall elements staggered in the depth direction have wall heights differing from one another.
 24. A method of producing a dyke as claimed in claim 12 comprising: incorporating a trench which extends from one of a dyke crown and the slope into a depth of the dyke body and in a longitudinal direction of the dyke; filling the trench with a protective wall made of a construction material consisting of mineral aggregates and an organic adhesive; compacting the construction material; and curing the construction material.
 25. The dyke as claimed in claim 15, wherein the protective wall projects at least partly into the slope. 